Lathe chuck mounting



J y ,1 P. B. LEVlTT LATHE CHUCK MOUNTING Filed Aug 29, 1940 2 Sheets-Sheet 1 INVENTOR PERCY 8. LEV BYfi Z l ATTORNEY July 21, 1942.

LATHE CHUCK MOUNTING P. B. LEVITT Filed Aug. 29, 1940 2 Sheets-Sheet 2 INVENTOR- PERCY B. LEV ITT BY ATTORNEY Patented July 21, 1942 UNITED STT ATET OFFICE LATHE CHUCK MOUNTIN G Application August 29, 1940, Serial No. 354,703

1 Claim.

This invention relates to an improvement in lathes designed to permit easy adaptation thereof to the cutting of shapes and bores of elliptical section.

A particular object of the invention is to provide an improved chuck mounting attachment for a lathe by means of which shapes and bores of elliptical section may be cut by a conventionally mounted cutting tool.

A more specific object is to provide a lathe chuck mounting attachment for cutting elliptical shapes or bores which is adjustable to vary the ratio between the major and minor axes of the ellipse.

With the foregoing and other objects and features in view, the invention consists in the improved lathe chuck attachment which is hereinafter described and more particularly defined by the accompanying claim.

In the following description of the invention reference will be made to the attached drawings, in which:

Fig. 1 is a transverse section of a lathe chuck attachment embodying the invention in a simplified form, taken on the plane l-I of Fig. 2;

Fig. 2 is a longitudinal section takenalong the line 22 of Fig. 1;

Fig. 3 is a vertical section along the line 33 of Fig. 1, looking in the direction of the arrows;

Fig. 4 illustrates diagrammatically how different portions of the periphery of a shape of elliptical section are successively presented to a stationary cutting tool during one half revolution of the chuck.

Fig. 5 is a vertical sectional view of a lathe chuck attachment designed in accordance with a preferred embodiment of the invention.

Fig. 6 is a cross section taken on the plane S6 of Fig. 5, looking down from above.

Fig. 7 is a view in end elevation showing the apparatus of Fig. 5.

Fig. 8 is a vertical section taken on the plane 8-8 of Fig. 6, looking in the direction of the arrow.

Fig. 9 is a side elevation of the apparatus at a reduced scale.

In Figs. 1, 2 and 3, a simple design of lathe chuck attachment is shown, in which the dimensions and locations of the various parts are fixed, so that an attachment assembled from such parts can only be used for cutting elliptical shapes and bores in which the major and minor axes of the ellipse have a definite ratio. In the drawings, the same or equivalent parts bear like numerical designations.

In the drawings l0 designates a lathe cutting tool having a conventional mounting; l2 designates a Work holding chuck of conventional design; and I4 designates a threaded end of the conventional head stock spindle.

The present invention is particularly concerned with the parts or elements for operatively connecting chuck [2 to the end of spindle M for rotation thereby. For this purpose a circular adapter plate 16 is shown having a centrally bored hub, the bore of which is internally threaded to engage threads on the end of the spindle. Chuck I2 is removably mounted on and operatively connected to the front face of plate It by means of dovetail joint IS. The chuck is provided with an element 20 having an extension of its rear face shaped to form a tongue element of the joint l8 which engages a correspondingly shaped and dimensioned groove in the face of the plate. Element 20 is shown as generally rectangular in shape and as having a length somewhat greater than the diameter of plate 16.

In Figs. 1, 2 and 3 a split eccentric ring 22 has been shown as encircling the hub of plate It and as having its front face in abutting relation to the rear face of the plate 16 along a bearing surface 24. Eccentric 22 is shown as held in abutting relation to plate It by a circular V- groove bearing 26 between the hub of plate I6 and the inner edge of ring 22. While not illustrated, bearing 26 should preferably incorporate an adjusting element to prevent lost motion; as by inserting a take-up ring wedge held by a lock nut between the hub of plate l6 and the inner circumference of eccentric 22. During rotation of spindle I4, plate [6 and chuck l2, eccentric 22 is prevented from rotating by an anchor pin and arm 28 which is connected to a stationary part of the lathe, such as the bed plate. Eccentric 22 has a circular external periphery 30 which is dimensioned to match and register with the inner wall of a circular follower ring 32. Follower ring 32 has been shown as having ears or projections 34 on its external periphery at opposite sides of one diameter thereof. The dimension of the ring at this diameter, including the projections of the two ears beyond the ring circumference, substantially equals the length of element 29 of the chuck. Clamping straps 36 and bolts 31 are shown as connecting the chuck and the guide ring 32 into a unitary structure which rotates with spindle I4. In Fig. 1 the longitudinal axis A of eccentric 22 is shown as positioned on diameter 22, and the longitudinal axis of spindle l4 and plate It is at B. In Fig. 3 the sum of the two clearance spaces 38 between the outer circumference of plate It and the straps 36 should slightly exceed the eccentricity AB of the ring 22 with respect to plate Hi. In operation, adapter plate It rotates relative to stationary eccentric 22 over lubricated bearing surfaces 26 and 24. Likewise follower ring 32 rotates relative to the eccentric over the lubricated cylindrical bearing surface 30. Element 20 of the chuck rotates With plate It, but also reciprocates relative thereto within the groove of the lubricated dovetail joint 13. This reciprocatory movement of the chuck is imparted theretdby the follower ring in rotating about theeccentric; the follower ring rotating with the adapter 'plate while at the same time reciprocating relative thereto over the lubricated bearing surface-24' thereof, in a path equal in length to the eccentricity AB of the eccentric.

An article-to which an elliptical shape --is to be given, is centered in the grip of the chuck jaws, and cutting tool- It -is advanced to a stationary cutting position normal to the article surface and at the right side-of-the apparatus, as portrayed by Fig- 1. For cutting elliptical shapes, the cutting tool should-always be placedonthat side of the work which corresponds with the side of ring22 ofgreatest eccentricity with-- For. cutting respect to axis B of the spindle. elliptical bores the cutting tool shouldbe located on that side of the object to be bored which is aligned with the side -f-minimumeccentricity. As the article being shaped is rotated in a counterclockwise direction Fig; 4 illustrates diagrammatically the various positions assumedby a shaped'endthereof during a half revolution of the chuck relative to a stationarycutting tool It.

Outline 39 in Fig. 4 shows the initial position;"

by asimple adjustable-eccentric guide. ring mounting rather than by having to change eccentricsa Referring to Figs-5, 6, 7,8 and '9, the threaded end of a head stock spindle I4 is shown as journaled by-a head-stockbearing 44, and as en gaged by. the threaded .bore of-the circular adapter plate It. A chuck l2 of conventional design is provided with a-carr-ier element having a tongue extension of its. rear face which is shaped and dimensioned to reciprocally engage a groove of corresponding shape and dimension in the front face of plate -|6,-thereb providing a dovetailjoint 18. The eccentric'element has been illustrated as including a-cylindrical member 46 having its walls encircling spindle l4, and having. a squared end which is tongued to fit in corresponding. grooves in bearing 44, to form a dovetail joint ML. A circular ball bearing race 50 is mounted on the external periphery of the cylinder. 45.. As. viewedin Fig. 5, the longitudinal axes of cylinder-ll6,,,ball race .50 and spindle. are alldisposedinthe samehorizontal. plane.

65. However, as the apparatus is portrayed in Fig, 6 in a cross section taken on the plane 66 (see also Fig. 8), the longitudinal axes of member 46 and ball race 53 are shown to be in a position A which is eccentric to the major axis B of spindle it in the plane fifi. In order to be. able to vary the eccentricity of the ball race 59 with respect to the spindle M, two adjusting bolts 52 are provided, each threadably mounted in brackets 55 which are positioned on opposite sides of bearing all in the plane 6% at right angles to the dovetail joint 43. By means of bolts 52 the tongue element at the squared end ofcylinder at can be moved in the corresponding groove of. the dovetail joint 48 to shift the axis A of the ball race 50 relative to the axis B of the spindle, in the plane 6-6. Brackets 5 have been shown as rotatably mounted in threaded apertures at the periphery of bearing 45, so that they ma be readily removed or shifted to one side when it is desi-red tomount or dismount cylinder 45 in -the dovetail joint 48.

Ball. race58 forms the eccentric guideunit of the apparatus shown in Figs. 5 to 9; and'a follower ring 32 is provided. which carries on its inner circumference a circular ball race 55 which is disposed .in coaxial relation encircling ball race 5%, to form a ball bearing having-its axis of rotation at point A of Fig- 8. Followerring 32 is attached to element 23 by extension straps or bracketsttwhich are-shown asextendingoutwardly and laterally-from opposite ends. of chuck element 2&1.

The operation of the apparatus of Figs. 5.to

9 should-be readily apparent from the priordescription. By means of bolts 52 the eccentricity of guide t6 and bearing race fiil can be varied so as to adjust the ratio between the major and minor axes of an elliptical shape hrv bore to that which it is desired to cut. After-the eccentricity has been set, and after the article to be shaped has been centered and gripped in the-jaws of the chuck, the cutting toolis brought into'contact with the. article on that .side of --axis 3 on which. lies the eccentric axis-A (Figs. 6, 7 and 8). As adapter plate It rotates-about axis B of spindle IA, follower ring 32 simultaneously rotates on its ball-bearing around the stationary eccentric 53. Thus at the sametime that chuck l2 rotates with plate l6, itis also forced to reciprocate within the groove .ofthe joint is .in following the .eccentric path of rotation of the follower 32..

The invention having been thus described in its preferred. form, what-is claimed. as newis:

An elliptical motion. lathe chuck attachment comprising arr-adapter plate arranged for coaxial mounting onalathe spindle a work holding chuck, a mounting joint between:the chuck and platearranged to allow the longitudinal axis of the chuck to reciprocate in a path normal to the axis. ofrotation of the-plate, a stationary guiding element havinga circular rolling bearing race with an axis located in a line eccentric to the and chucklinto, aunitary structure arranged. to

continuously reciprocate the chuck with respect to theadapter plate while simultaneously rotating the chuck as a unitwith theplate.

PERCY BIGMORE, LEVTTT.1 

